1. Field of the Invention
The present invention relates to an external combustion engine generating and liquefying steam of a working fluid, using the accompanying change in volume of the working fluid to displace a liquid part of the working fluid, and converting this to mechanical energy for output.
2. Description of the Related Art
In the past, this type of external combustion engine has also been called a “liquid piston steam engine”. A working fluid is sealed in a pipe-shaped main container flowably in a liquid state. Part of the liquid state working fluid is heated to evaporate at a heating portion formed at one end of the main container, while the steam of the working fluid is cooled to condense at a cooling portion formed at the intermediate part of the main container. By alternately repeatedly evaporating and condensing this working fluid, the liquid phase part of the working fluid is made to cyclically displace (so-called “self vibration”) and the self vibration of the liquid phase part of this working fluid is taken out at the output part as mechanical energy (for example, see Japanese Patent Publication (Kokai) No. 2007-255259).
This art aims at controlling the average value of the internal pressure of the main container so as to approach the target value. Therefore, it can improve the output and efficiency of the external combustion engine. More specifically, by sealing the working fluid in an auxiliary container separate from the main container in the liquid state and connecting the main container and the auxiliary container through a venturi, the internal pressure of the auxiliary container is stabilized at a pressure substantially equal to the average value of the internal pressure of the main container.
Further, the target value of the average value of the internal pressure of the main container is calculated based on the temperature of the heater etc. and the working fluid in the auxiliary container is compressed or expanded by the piston mechanism so as to control the internal pressure of the auxiliary container to approach the target value. By doing this, the average value of the internal pressure of the main container is made to change to track the internal pressure of the auxiliary container and approach the target value.